1. Field of the Invention
The present invention relates to an engine control device, and more particularly to a control device that simultaneously assures satisfactory startup performance and exhaust performance.
2. Description of the Related Art
It is being demanded that engine exhaust emissions be further reduced in accordance with increasingly stringent automotive engine exhaust emission control, for instance, in North America, Europe, and Japan. Due to enhanced catalyst performance and increased catalyst control accuracy, engine exhaust emissions mainly depend on the amount of exhaust at startup. In a control process that is initiated while the engine is stopped and then continued to maintain the engine speed at an idling level, a method of allowing the engine speed to overshoot the idling level, then reducing the engine speed to the idling level, and maintaining such an idling engine speed is employed for the purpose of achieving proper engine startup. Exhaust emission control is exercised to restrict the exhaust amounts [g] of HC, CO, NOx, and the like. However, since the intake air amount for startup unduly increases due to the above-mentioned engine speed overshoot, the exhaust amounts of HC, CO, and NOx increase excessively. Under the above circumstances, there is a need for optimizing the intake air amount for startup.
An invention disclosed in JP-A-2002-213261 minimizes such a startup intake air amount by setting the engine startup intake amount of each cylinder to a minimum value that achieves ignition.